1. Field of the Invention
The present invention is generally related to a cooling system for a marine propulsion device and, more particularly, to a cooling system valve that selectively routes cooling water to portions of the marine propulsion system based on the magnitude of incoming water pressure from a water pump.
2. Description of the Related Art
Those skilled in the art of marine propulsion systems are familiar with many systems and devices that are utilized to appropriately direct and/or restrict the flow of cooling fluid through conduits of the marine propulsion device. Some devices are provided to inhibit disadvantageous flow while others are used to encourage advantageous flow.
U.S. Pat. No. 6,368,169, which issued to Jaeger on Apr. 9, 2002, discloses a marine engine cooling system with a siphon inhibiting device. A valve is provided for a marine engine cooling system and the purpose of the valve is to prevent the draining of the pump and outboard drive unit from creating a siphon effect that draws water from portions of the cooling system where heat producing components exist. The valve also allows intentional draining of the system when the vessel operator desires to accomplish this function. The valve incorporates a ball that is captivated within a cavity. If the ball is lighter than water, its buoyancy assists in the operation of the valve.
U.S. Pat. No. 6,439,939, which issued to Jaeger on Aug. 27, 2002, discloses a siphon inhibiting device for a marine cooling system. The siphon inhibiting valve comprises first and second portions of a housing structure and a buoyant member disposed within the housing structure for movement along a first axis between an inlet port and an outlet port. The buoyant member is shaped to have a cylindrical portion and another portion which is shaped in the form of a frustum of a cone. Upward movement of the buoyant member causes an elastomeric seal on the buoyant member to come into contact with an internal lip formed in the housing structure, thereby creating a seal that prevents an upward flow of water in a direction from the outlet port to the inlet port.
U.S. Pat. No. 6,379,201, which issued to Biggs et al. on Apr. 30, 2002, discloses a marine engine cooling system with a check valve to facilitate draining. The cooling system is provided with a valve in which a ball moves freely within a cavity formed within the valve. Pressurized water, from a sea pump, causes the ball to block fluid flow through the cavity and forces pumped water to flow through a preferred conduit which may include a heat exchanger. When the sea pump is inoperative, the ball moves downward within the cavity to unblock a drain passage and allow water to drain from the heat generating components of the marine engine.
U.S. Pat. No. 6,652,337, which issued to Logan et al. on Nov. 25, 2003, discloses an exhaust system for a marine propulsion engine. By providing a space between surfaces of a raised exhaust portion of the components and surfaces of the raised coolant portions of the exhaust system, leakage from the coolant conduits to the exhaust cavities is avoided. The space provided between exhaust portions of the manifold and elbow and coolant portions of the manifold and elbow, near the joint between these components, provides the two advantages of maintaining a higher exhaust connection between the manifold and the elbow and also preventing coolant leakage from flowing from the coolant passages to the exhaust passages of the exhaust system.
The patents described above are hereby expressly incorporated by reference in the description of the present invention.
In marine propulsion systems, it is important that cooling water be provided to remove heat from heat emitting portions of the system. However, the provision of cooling water must be provided in such a manner that certain components are not cooled to temperatures lower than desirable thresholds while other components are not deprived of sufficient cooling water flow to maintain their temperatures below upper thresholds. If cooling water, typically from a lake or body of water in which a marine vessel is operated, is provided at a rate higher than desired, certain components can be cooled below advantageous temperatures and this overcooling can result in condensation of moisture within those components. Therefore, it is desirable to limit the flow of cooling water to those components when the engine is not operating at sufficient speeds to generate heat commensurate with the cooling water flow. Alternatively, when an engine is operating at higher speeds, it is necessary to provide cooling water at a sufficiently high flow rate to prevent overheating those components. It would therefore be beneficial if a cooling system could be provided that simply and efficiently controls the flow of water between alternative paths in order to avoid the overcooling of certain components and the overheating of other components. It would be further beneficial if such a system could vary the direction of cooling water flow as a function of the rate of flow of the cooling water provided by a pump that draws the water from a body of water.